Process for simultaneously stabilizing and applying a vat dye to textile material comprising regenerated cellulose



?atenteci Feb. 10, 1953 PROCESS FOR SIMULTANEOUSLY STABILIZ- ING ANDAPPLYING A VAT DYE TO TEX- TILE MATERIAL COMPRISING REGENER- ATEDCELLULO SE Leslie L. Walmsley, Ridley Park, and Raymond E.

Smith, Chester, Pa., assignors to American Viscose Corporation,Wilmington, Del., 9. corporation of Delaware No Drawing. ApplicationNovember 25, 1949, Serial No. 129,498

8 Claims.

1 This invention relates to a method of stabilizing textile materialagainst progressive dimensional shrinkage on repeatedv laundering andagainst normal pulling out during final finishing operations,simultaneously with the application of a vat dyestuif to the textile.material.

Normally treatment of a textile material, such as a regeneratedcellulose fabric, for example. and the application of a vat dyestuffthereto, involves a two-step process in which the fabric is dyed in oneoperation and then treated for the purpose of stabilizing it. In thisconventional two-step process, the fabric is first dyed in an operationcomprising the following steps:

1. Preparation of the fabric for dyeing by desizing, scouring, rinsingand drying the fabric;

2. Application of the vat dyestuif to the fabric by padding;

3. Reduction of the pigment to the leuco vat;

4. Oxidation of the leuco vat to the vat pigment;

5. Securing of the fabric following the oxidation step;

6. Drying;

7. Framing the fabric to the desired width.

After step 7 has been performed, the fabric is subjected to a treatmentintended to stabilize it against shrinkage, a synthetic resin beinggenerally used as the stabilizing agent. This treatment involves thefollowing steps.

8. Application of the resin to the fabric by padding;

9. Drying of the resin-treated fabric;

10. Curing the resin on the fabric to an insoluble condition;

11. Securing of the fabric carrying the cured resin;

12. Drying the fabric; and

13. Framing the fabric to desired Width.

The present invention, in accordance with which textile materials areeffectively stabilized against both progressive dimensional shrinkage onrepeated laundering and pulling out during finishing, simultaneouslywith the application of a vat dyestuif, comprises the following steps;

1. Preparation of the fabric by desizing. scouring and drying;

- 2. Simultaneous application of the vat pigment and a specialstabilizing medium;

3. Drying;

4. Curing of the stabilizing medium;

5. Reduction of the pigment to the leuco vat;

6. Oxidation of the leuco vat back to the vat igment;

7. scouring after the oxidation;

8. Drying; and

9. Framing to desired width.

As will be apparent, by the method of this invention, four of the stepswhich are'required in the normal practice of the trade are entirelyeliminated, which reduces the handling and time required to prepare thetextile material .for the market, and considerably lessens the cost ofthe fabric by substantial reduction in both the labor and operatingcosts.

Since the present invention is of special importance in the treatment offabrics formed from or comprising fibers, filaments, or yarns ofregenerated cellulose, including yarns predominantly of spun viscoserayon, it will be discussed in detail in connection with the treatmentof such fabrics.

The trade has never been successful in oncetively stabilizing aregenerated cellulose fabric against both progressive dimensionalshrinkage on repeated laundering and the pulling out which normallyoccurs whensuch fabrics are subjected to final finishing, simultaneouslywith the application of color to the fabric. The stabilizing agentsavailable to the trade have not been entirely satisfactory. For example,cellulose ethers, which have been proposed as stabilizing agents, imparta measure of stability against progressive dimensional shrinkage'onrepeated laundering to the fabric, but do not stabilize it againstpulling out during final finishing. Moreover, most of the treatmentswhich have been depended upon to impart stability to the fabric haveinvolved the use of substances which are not compatible with, or notadapted to use in conjunction with, the known dyestuffs.Urea-formaldehyde resin is one example of a substance which has beenconsidered for application to regenerated cellulose fabrics in the formof a precondensate and cured to the insoluble condition on the fabric.Regenerated cellulose fabrics cannot be dyed successfully with a vatdyestuif, for example, applied to the fabric in a treating mediumcomprising a urea-formaldehyde resin, because the resin retards thereduction of the dye to its soluble leuco form which must be effected onthe fabric after the resin is cured. Other resins of this type have thesame or similar disadvantages. The retarding or inhibiting eifect of theresins on reduction of the vet dyestuffs on the fabric is one factorresponsible for the fact that stabilization of. the fabricsimultaneously with the application of color thereto by means of a vatdyestuff has remained a desirable objective which, however, has notdyeing is obtained by a mere mechanical fixing ofthe dye on the surfaceof the fabric by fixing of the ether thereon. Up to the present, the

common practice in the trade has been the old.

one of dyeing the fabric inone oper'ation and then treating the dyedfabric with a medium in-' tended to impart stability thereto, in aseparate, different operation, as outlined in detail above. I

The primary object of this invention isto provide a novel process inwhich textile niaterials, particularly those predominantly of regenerated cellulose, are stabilized against both progressive dimensionalshrinkage on repeated laundering and normal pulling out during finalfinishing in the stabilized condition and dyed simultaneously, using anaqueous treating liquid containing both the dyestuff and the stabilizingmedium. Another object is to dye and stabilize the textile materialscomprising or consisting of regeneratedcellulose with minimumdegradation or the cellulose and loss in tensile strength. A specificobject is to dye and stabilize the textile materials, using a treatingliquid containing a vat pigment and stabilizing media which do notretardor inhibit reduction of the vat pigment to thesoluble leuco vat onthe fabric. Other objects and advantages of the invention will beapparent from the following description. I

We have now found that textile material's, particularly of regeneratedcellulose, can be successfully stabilized against both progressivedimensional shrinkage on repeated laundering and normal pulling outduring final finishing subsequent tothe stabilization, simultaneouslywith application; of color thereto, provided thatthe stabilization iseffected by me'ans of a waterinsoluble, alkali-soluble cellulose etherand forz'naldehyde applied conjointlyto the textile materialwith thedyestuff under specific controlled conditions as set forth herein. I

In, accordance with the invention, textile materials, particularlyfabrics predominantly of regenerated cellulose, are impregnated ortreated with an aqueous treating medium having a pH of from 1.2 to 6.5and containing the dyestuff, the water 'insoluble, alkali-solublecellulose ethen, and formaldehyde, dried in the absence of contactpressure and preferably under tension, heated in the absence of contactpressure to cure the aldehyde, and after-treated, if necessary, todevelop thedye on the fabric.

In the presently preferred embodiment of the invention, the dyestufiapplied to the fabric in the aqueous treating liquid containing thewaterinsoluble, alkali-soluble cellulose ether and formaldehyde forstabilizing the fabric, is a vat pigment. Under the conditions of thisprocess, the cellulose ether and aldehyde, which function conjointlytostabilize the fabric, after curing of the aldehyde, do not retard orinhibit reduction of the pigment vat to the soluble leuco vat on thefabric, or regeneration of the dye by oxidation. After the fabric isheated to curing temperature for the formaldehyde and then treated forreduction of the insoluble vat pigment to the soluble leuco vat,followed by oxidation for regenerating the dye on the fabric, the fabricis effectively -In .a preferred embodiment,

4 light and wash fastness. The results of the present process aredifferent from the results which may be obtained by treating textilematerial with a pre-dyed cellulose ether. In this process, the fabric isstabilized effectively against both progressive dimensional shrinkage onrepeated laundering and pulling out during final finishing, and thefibers of the fabric are dyed in cross-section, whereas fabrics tr atedwith a pre-dyed cellulose ether are not effectively stabilized againstpulling out during final finishing, and

the fibers of the fabric are not dyed in cross-secf aecordance with thisembodiment is prepared by mixing the water-insoluble, alkali-solublecellu-- lose ether with an aqueous alkaline solution, for example, withan aqueous solution of sodium hydroxide, dispersing the insoluble vatpigment through the mixture, and then' adding the formaldehyde. The pHof the final mixture is on the alkaline side, usually'between l2 and i4,and a pH regulator, for example a'strong mineral acid such as sulfuricacid, is added in an amount sufficient to neutralize the alkali andreduce the pH to a value in the range of from 1.2 to 6.5. Generally,sulfuric acid maybe added in an amount of from 1.7 to 2.9% by weight,which is in excess of the amount required to neutralize the alkali andconvert it to the corresponding alkali metal sulfate, the excess acidserving as a curing or condensing catalyst for the aldehyde when thefabric is heated to curing temperature. The acid may be added to thealkaline medium at room temperature or at temperatures below roomtemperature. I

In practicing the preferred embodiment of the invention, the aqueoustreating medium having a pH of from 1.2 to 6.5 and containing thecellulose ether, dispersed vat pigment, and formaldehyde is applied tothe fabric to be dyed and stabilized while the fabric is held undertension, for example by padding, and the fabric is dried 7 undertension, for example on the tenter, at a temperature of 240 5". orbelow, for instance between 200 and 240 The dried fabric is then heatedat a temperature of 300 F. to 350 F. for a time interval generallyinversely related to the temperature, to convert the aldehyde to theinsoluble, set condition and to coagulate the cellulose ether. Thedrying and curing are performed in the absence of pressure. The fabricis heated to cure the aldehyde while it is on a tenter or the like, byblowing hot air on the fabric. Preferably, the curing is performed whilethe fabric is tensioned, but this is not essential, whereas applicationof the treating liquid and drying of the treated fabric are performedunder tension for optimum results.

The vat pigment may be reduced to the soluble leuco vat on the fabric,after the aldehyde has been cured and the ether coagulated, by the usualmethods of reducing vat pigments, for example by treating the fabricwith an aqueous solution of sodium hydroxide and sodium hydrosulflte incontrolled amounts. Regeneration of the pigment may be effected bytreating the fabric carrying the reduced vat with an aqueous solution ofa mild oxidizing agent, for example, sodium perborate.

the treating medium also comprises an agent which exerts a softening orplasticizing action on the cured aldehyde, on the textile material, oron both. The

'plasticizer may be added to the medium at either alkaline or acid pH,but is normally added after the dyestuff has been dispersed in theaqueous alkaline medium containing the water-insoluble, alkali-solublecellulose ether.

The aqueous treating medium having a pH from 1.2 to 6.5 contains from0.5 to 1.5%, preferably about 1%, of the w-ater-insoluble,alkalisolublecellulose ether, from 0.01 to 5% of a vat dyestuif, from 1 to 5%,preferably about 3% of formaldehyde, and from 0.5 to 1.5% of theplasticizing agent, the percentages given being by weight based on theweight of the treating medium. The treating liquid also contains sodiumsulfate which functions as a buffer to prevent tendering of the fabricby the sulfuric acid catalyst during baking thereof to cure theformaldehyde. Prior to neutralization of the alkali, it is present inthe medium in a concentration of from 0.5 to 1.5%.

The term water-insoluble, alkali-soluble cellulose ether" includes suchethers which are insoluble in water but soluble in aqueous alkalisolutions of from 1 to 8% concentration at room temperature or atreduced temperature, including simple alkyl ethers, carboxyalkyl ethers,hydroxyalkyl ethers, mixed alkyl hydroxyalkyl ethers, mixed alkylcarboxyalkyl ethers and the salts of the earboxyalkyl ethers.Hydroxyethyl celluloses having a standard viscosity of from 0.05 to 2,and an average degree of substitution of from 0.10 to 0.40 ethyleneoxide group per anhydroglucose unit are satisfactory. The standardviscosity is that of solutions containing 85% water, 6% of the celluloseether, and 9% sodium hydroxide by weight, measured at 25 C. andexpressed as a multiple of the viscosity of glycerol at 25 C.

The aqueous medium may be an aqueous solution of a strong inorganicalkali, such as sodium, potassium, or lithium hydroxide. Preferably, thecellulose ether, the vat pigment, and the formaldehyde are mixed with anaqueous solution of sodium hydroxide, in the order named. The

ether. may be dissolved in the alkaline medium in I a concentrationhigher than that desired finally, and the solution may then be dilutedto the desired concentration. The pH regulator which is added to thetreating medium may be any acid or salt which adjusts the pH to 1.2 to6.5. Sulfuric acid is presently preferred. Surprisingly, when sulfuricacid is added to the aqueous medium containing the ether, dyestuif, andformaldehyde in an amount sufiicient to adjust the pH to 1.2 to 6.5,

. the ether is not visibly precipitated, in spite of the fact thatsulfuric acid is known to be a precipitant 1 for these ethers.

Any vat dyestuff, whether of the anthracene, indigoid, or sulphide typedyestuffs, may be added to the aqueous alkaline medium containing thewater-insoluble, alkali-soluble cellulose ether, and formaldehyde. Theinsoluble pigment vat is added to the alkaline ether solution ordisperwith andchemically inertto the. remaining iii-- gredients of themedium. Examples of suitable plasticizing or' softening" agents are theethers and, esters of polyhydric alcohols'containing one or more.freehydroxyl groups, and condensates thereof with ethylene oxidecontaining for'example from 1 to 50 ethylene oxide units per molecule.For instance,,the self-emulsifying wax-like material used asplasticizing agent may be a butyl ether of a polyhydric' alcohol such asethylene glycol monobutyl ether, a partial ester of an inner anhydrideof a polyhydric alcohol with a. fatty acid containing, preferably, atleast 8 carbon atoms, or condensates thereof with ethylene oxide; or itmay be a partial ester of such alcohols as sorbitol, mannitol,.glycerol, glycol, etc. with a fatty acid such as stearic, oleic,myristic, lauric, etc., or condensates of the esters with ethyleneoxide. A particularly effective, preferred plasticizing agent comprisesa-mixture of 50% sorbitan monopalmitate and 50% sorbitan tristearatecontaining 16 polyethylene oxide units per molecule. In certaininstances, the plasticizing agent may be omitted, as for instance when adyed textile of less pronounced flexibility is desired for" any reason,or when a cellulose ether of low viscosity is used.

By the process of this invention, the difiiculties encounteredpreviously when it was attempted to stabilize a regenerated cellulosefabric against both progressive dimensional shrinkage on laundering andpulling out during final finishing, simultaneously with the' applicationof color thereto, are overcome. The results'obtained by the practice ofthe invention depend on the conjoint use of the water-insoluble, alkalisoluble cellulose ether and formaldehyde for stabilizing the fabric, andare not obtainable by applying a vat dyestufi to the fabric inconjunction with other agents which have been proposed for impartingstability'to a regenerated cellulose textile. An unexpected and uniquefeature of the present process is that a pigment vat can be reduced tothe soluble leuco vat on the fabric in spite of the presence of thecellulose ether and aldehyde on the fabric, and after heating of thefabric to cure the formaldehyde to insoluble condition and coagulate theether, whereas ureaformaldehyde and similar resins which are condensedon the fabric function as a resist to retard or inhibit reduction of apigment vat to a soluble leuco vat. 'The pigment applied to the fabricsimultaneously with the water-insoluble, alkalisoluble cellulose etherand formaldehyde in a treating liquid having a pH of 1.2 to 6.5, inaccordance with this invention is completely and uniformly reduced tothe soluble condition on the fabric, and stabilized fabrics which aredyed to level shades of excellent fastness are obtained.

Fabrics dyed and stabilized in accordance with the invention aredimensionally stable on repeated washing and compare very favorably asto shade and fastness with fabrics dyed with the vat dyestuif in oneoperation and subsequently stabilized by treating them with an aqueoustreating liquid having a pH of 1.2 to 6.5 and containing the celluloseether and formaldehyde.

The following non-limiting'examples are given as illustrative ofspecific embodiments of the invention.

EXAMPLE I sodium hydroxide was added, 2.5 lbs. of the caustic solutionbeing used. 0.5% of the vat dyestufi Indanthrene BlueBCSN Dbl. Paste(Pr. 115) was pasted in 3 .gallons of water and mixed with the alkalinesolution containing the cellulose ether. One pound of a mixture.consisting of 50 sorbitan monopalmitate and 50% of sorbitan tristearatecontaining 16 polyoxyethylene units dissolved in 3 gallons of water wereadded. Twenty pounds of formaldehyde (as 37% commercial formalin) werestirred in, and the mass was diluted with water to 21 gallons. A 20%solution of sulfuric acid was added to adjust the pH to 1.30, and waterwas added to give 24 .gallons of treating medium which was .strainedintoa pad trough to remove any foreign matter.

A plain weave 100% regenerated cellulose ohallis fabric in the greige,made of 80 warp and 60 filling yarns was desized, boiled off,.anddriedon a pin tenter. The resulting white fabric had a'count of 84 by 64, andweight of 4.0 ounces per yard.

The fabric was padded through the treating solution under tension,pick-up at the pad being about 85 frame, fed to a tenter without usingoverfeed, and treated on the .tenter to cure the formaldehyde by blowinghot air (330 F.) against the fabric for 2 minutes. The fabric was thenimmersed for 15 minutes in a reducing bath having 5 a temperature of 140F. and containing 15% sodium hydroxide and 0.3% of sodium hydrosulnte,and then immersed for 15 minutes in an oxidizing bath having atemperature of 120 1+.

and containing 0.12% of sodium perborate. The 1- Wa-rpwz'se shrinkageper cent on washing (Standard OCC-T-lQIA Cotton Wash Test) Filth Wash-'ing Fourth Washing Third Wash- *ing Second W ashing First Washing Dyedand Stabilized Percent Percent Percent Fabric (Ex. 1) 0.0 --0 6 0.0

UutreaicdFabric... -2.5 -2I7s The stability imparted to the fabric bythe cellulose ether and formaldehyde conjointly is superior to thestability which can be obtained by treating a regenerated cellulosefabric with either formaldehyde or the cellulose ether alone, althoughthe reasons for .thisare .not .rea-dilyapparent. It may bezthat thecellulose ether assists in retarding or'hastening conversion of theformaldehyde to the insoluble condition .so that the latter iscured-when thegelstructure of the film or coating on or in the:regenerated cellulose fabric or the like is in an optimum condition ofswelling. It is possible, also, that during the curing step, theformaldehyde reacts chemically with the free hydroxyl groups of thecellulose ether and/or with the hydroxyls of the regenerated cellulosetextile material. Such reactions may, in fact, beinitiated during thedrying step. In any case, the dried fabric comprises a heat- The fabricwas then dried on a. clip r convertible composition comprisingformaldehyde, which is converted to insoluble, set condition when thefabric is heated to the curing temperature.

EXAMPLE II Example I was repeated, except that the treating mediumcontained the vat dyestuff Indanthrene Yellow 3 RD Die. Pst. (C. I. No.1118).

EXAMPLE III The procedure was the same as in Example I, the treatingmedium comprising the ether, formaldehyde, and Calcosal Jade Green NPDle. Paste. (C. I. No. 1101).

Since some variations made in practicing the invention, withoutdeparting from the spirit and scope thereof, it will be understood thatthe invention is not to be limited except as defined by the appendedclaims.

We claim:

1. A method of stabilizing textile materials predominantly ofregenerated cellulose against progressive dimensional shrinkage underrepeated washings and against normal pulling out during final finishingoperations performed subsequently to the stabilization andsimultaneously applying color to the textile which comprises wetting thefibers of the material with a fluid aqueous medium having a pH between1.2 and 6.5 and containing a Water-insoluble alkali-soluble celluloseether, a dispersed vat pigment and formaldehyde, drying the textilematerial in the abscnce of contact pressure, heating the dried textilematerial in the absence of cont-act pressure to cure the formaldehyde,treating the textile material, after said heating step, with an aqueousalkaline solution to reduce the vat pigment to the soluble leuco vat onthe textile material, and then treating the textile material with anaqueous solution of a mild oxidizing agent to regenerate the pigment onthe textile material.

2. A method as in claim 1, wherein the fibers of the textile materialare wetted with the treating medium containing the water-insoluble,alkali-soluble cellulose ether, the dispersedpigment vat, and theformaldehyde, while the material is under tension.

3. A method as in claim 1, wherein the textile material i dried undertension.

4. A method as in claim 1, wherein the formaldehyde is cured and theether is coagulated by blowing hot air against the textile material.

5. A method as in claim 1, wherein the waterinsoluble alkali-solublecellulose ether is a hydroxyethyl cellulose.

6. A method as in claim 1, wherein the aqueous treating medium contains,by weight, from 0.5

- to 1.5% of the water-insoluble, alkali-soluble cellulose ether, from0.01 to 5% of the dispersed pigment vat, and from 1 to 5% offormaldehyde.

'7. A method as in claim 1, wherein the regenerated cellulose textilematerial is a woven fabric.

8. An aqueous treating medium for stabilizing textile materialspredominantly of regenerated cellulose against progressive dimensionalshrinkage on repeated laundering and against pulling out in response .totension applied subsequently to the stabilization while simultaneouslyapply- REFERENCES CITED The following references are of record in thefile of this patent:

Number 10 UNITED STATES PATENTS Name Date Karplus July 6, 1926 PfefferApr. 23, 1929 Pfefier Jan. 21, 1930 Kantorowicz Aug. 4, 1931 Bolton Feb.8, 1938 Wolf Feb. 15, 1938 Heberleln June 18, 1940 Pinkney Feb. 16, 1943Weisberg May 18, 1948 OTHER REFERENCES Rayon Textile Monthly for January1945, pages 16 79 (25)-82 (28), article by D. M. Martin.

1. A METHOD OF STABILIZING TEXTILE MATERIALS PREDOMINANTLY OFREGENERATED CELLULOSE AGAINST PROGRESSIVE DIMENSIONAL SHRINKAGE UNDERREPEATED WASHINGS AND AGAINST NORMAL PULLING OUT DURING FINAL FINISHINGOPERATIONS PERFORMED SUBSEQUENTLY TO THE STABILIZATION ANDSIMULTANEOUSLY APPLYING COLOR TO THE TEXTILE WHICH COMPRISES WETTING THEFIBERS OF THE MATERIAL WITH A FLUID AQUEOUS MEDIUM HAVING A PH BETWEEN1.2 AND 6.5 AND CONTAINING A WATER-INSOLUBLE ALKALI-SOLUBLE CELLULOSEETHER, A DISPERED VAT PIGMENT AND FORM ALDEHYDE, DRYING THE TEXTILEMATERIAL IN THE ABSENCE OF CONTACT PRESSURE, HEATING THE DRIED TEXTILEMATERIAL IN THE ABSENCE OF CONTACT PRESSURE TO CURE THE FORMALDEHYDE,TREATING THE TEXTILE MATERIAL, AFTER SAID HEATING STEP, WITH AN AQUEOUSALKALINE SOLUTION TO REDUCE THE VAT PIGMENT TO THE SOLUBLE LEUCO VAT ONTHE TEXTILE MATERIAL AND THEN TREATING THE TEXTILE MATERIAL WITH ANAQUEOUS SOLUTION OF A MILD OXIDIZING AGENT TO REGENERATE THE PIGMENT ONTHE TEXTILE MATERIAL.